JP2002352611A - Lighting system and display device equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting system radiating illumination light having high directivity and uniform intensity distribution. SOLUTION: This lighting system is equipped with a light source device 11 and a light direction conversion device 12 directing the traveling direction of light beams emitted from the light source device 11 in the specified direction. The light source 11 contains a plurality of light sources 11a, 11b, 11c, and the light direction conversion device 12 contains a plurality of unit conversion elements 12a, 12b, 12c. Each unit conversion element is installed so as to correspond to each light source, and the light source is arranged on each optical axis OX of the corresponding unit conversion element. Each unit conversion element has a first conversion region M directing light beams incident from the corresponding light source among a plurality of light sources and light beams incident from at least one light source other than the corresponding light source to the specified direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device and an illuminating device, and more particularly to an illuminating device suitably used for a liquid crystal display device and a liquid crystal display device having the same.

[0002]

2. Description of the Related Art A liquid crystal display device uses a liquid crystal display element which does not emit light by itself, unlike an image display device such as a CRT, PDP or EL, so that illumination for irradiating the liquid crystal display element with light for displaying is performed. It has a device. For example, a transmissive liquid crystal display device has a planar illumination device called a backlight behind the liquid crystal display element (on the side opposite to the viewer), and transmits light emitted from the backlight to the liquid crystal display element. An image is displayed by controlling the amount of light for each pixel.

A liquid crystal display element of a twisted nematic (TN) type or a super twisted nematic (STN) type, which is a general liquid crystal display element, has a liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates, and a liquid crystal layer sandwiched between the liquid crystal layers. And a pair of polarizing plates disposed behind and in front of the liquid crystal layer. Of the light emitted from the backlight to the liquid crystal display element, the polarized light transmitted through the rear polarizer enters the liquid crystal layer, and the polarization direction is changed by the liquid crystal layer.
The amount of light transmitted through the front polarizer is controlled.

However, the quality of an image displayed on a liquid crystal display device changes depending on the angle at which the image is viewed, that is, the viewing angle. For example, there is a problem that a normal image cannot be obtained due to a change in contrast ratio, luminance and color tone of a halftone. This is because the liquid crystal molecules in the twisted liquid crystal layer are in a tilted state when displaying a halftone, so that the polarization direction of the light incident from the direction in which the liquid crystal molecules are tilted is relative to the long axis of the liquid crystal molecules. The light is almost perpendicular, and this light is not affected by birefringence. On the other hand, the polarization direction of light incident from other directions has a component parallel to the long axis of the liquid crystal molecules, and thus is affected by birefringence. As a result, the display light amount changes depending on the viewing angle.

In order to improve the viewing angle characteristics of the liquid crystal display device (ie, to reduce the viewing angle dependency), the directivity of illumination light is increased, and a light diffusing element is provided on the viewer side of the liquid crystal display element. A method is proposed in which a display image having a constant contrast ratio, a halftone luminance, and a color tone obtained by narrowing an angle range of illumination light incident on a display element can be observed from a wide viewing angle range by a light diffusion element. Have been.

For example, Japanese Patent Application Laid-Open No. 2-118518 discloses a liquid crystal display device 3 having a structure schematically shown in FIG.
00 is disclosed. The liquid crystal display device 300 includes a lighting device 310, a liquid crystal display element 320, and a light diffusion element 330.

[0007] The backlight 310 has a light source 311, a spherical mirror 312, and a Fresnel lens 313, and illuminates the liquid crystal display element 320. The spherical mirror 312 disposed so as to face the Fresnel lens 313 with the light source 311 interposed therebetween reflects light rays from the light source 311 toward the Fresnel lens 313, thereby improving light use efficiency.

[0008] Here, the Fresnel lens is not a spherical surface having a continuous refraction surface, but a plane lens on which a refraction surface (also referred to as a "prism surface") inclined stepwise is formed. As schematically shown, the prism array is a prism array in which prisms obtained by converting only the curvature of a lens into a prism shape are arranged on a plane. Therefore, when replacing a circular lens with a Fresnel lens, prisms are arranged concentrically, and when replacing a cylindrical lens with a Fresnel lens, prisms are arranged linearly. A prism formed on a Fresnel lens generally has a parallel surface substantially parallel to an optical axis and an inclined surface, and refracts light on the inclined surface to exhibit the properties of the lens. Since the Fresnel lens is a flat lens and is generally formed of a transparent resin such as an acrylic resin or a polycarbonate resin, the Fresnel lens has an advantage that the thickness of the lens can be reduced and the weight can be reduced.

The backlight 31 configured as described above
At 0, by arranging the light source 311 in the vicinity of the focal point of the Fresnel lens 313, the light beam from the light source 311 is refracted by the prism formed on the Fresnel lens 313 and travels in the front direction to obtain highly directional illumination light. Can be

The liquid crystal display element 320 receives the highly directional illumination light from the illumination device 310 and controls the light transmittance for each pixel to display an image. The light diffusion element 330 diffuses display light of an image that has passed through the liquid crystal display element 320, so that an image with little change in display quality is observed from a wide viewing angle range.

Japanese Patent Application Laid-Open No. 11-504124 discloses a light source 411 and total internal reflection (T
An illumination device 400 configured to irradiate highly directional illumination light constituted by an IR (IR) lens 412 is disclosed.

As shown in FIG. 21, the TIR lens 412 generally has a dome shape surrounding the focal point, and a large number of prisms are arranged on the surface facing the focal point. Each of the shapes is composed of a parallel surface substantially parallel to the optical axis and an inclined surface, but is roughly classified into two types of prisms by the action of the inclined surface.

That is, the prism formed in the vicinity of the optical axis (region R1) is a refraction prism that controls the traveling direction of light by refracting light on an inclined surface, similarly to the prism formed on the Fresnel lens. On the other hand, the prism formed in a region (region R2) far from the optical axis is a reflective prism that controls the traveling direction by reflecting the light that has entered inside on an inclined surface.

The light source 411 is a TI having the above-described configuration.
By arranging near the focal point of the R lens 412, the traveling direction of the light beam from the light source 411 is controlled by the refraction prism (region R1) and the reflection prism (region R2), and the front direction (the direction parallel to the optical axis) ) Is irradiated with highly directional illumination light.

[0015]

As a result of investigations made by the present inventors, the above-mentioned conventional illuminating device can provide illuminating light with high directivity, but solves the following problems in order to widen the illuminating range. I found it necessary.

First, the Fresnel lens 31 shown in FIG.
In order to illuminate a wider surface and improve the brightness of the illumination light, a plurality of light sources 311 ′ are arranged at regular intervals as shown in FIG. It is necessary to combine the Fresnel lenses 313 'in which one unit Fresnel lens 313'a is formed. That is, the traveling direction of the light beam from each light source 311 'is controlled by the corresponding unit Fresnel lens 313'a, and high-directional illumination light is emitted.

Therefore, if the brightness and color tone of the light source 311 'are different from each other, the brightness and color tone of the illumination light are different for each unit Fresnel lens 313a, so that the boundary of the unit Fresnel lens 313'a is clearly seen. I will. However, the light sources 311 'are controlled such that the light emission characteristics of the respective light sources 311' are controlled to be constant such that this can be avoided.
It is very difficult to manufacture or sort 11 '.

Similarly, in the lighting device disclosed in Japanese Patent Publication No. 11-504124, as shown in FIG. 23, a plurality of light sources 411 'and one unit TIR lens 412 are provided for each light source 411'. TIR with 'a formed
When the lighting device is configured by the lens 412 ′, the light source 4
The difference in brightness, color tone, etc. of the unit 11 ′ is a unit TIR lens 41
Reflected in the illumination light for each 2'a, the unit TIR lens 41
The boundary of 2'a is observed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a main object thereof is to provide a lighting device having high directivity and a relatively uniform intensity distribution, and a display device using the same. The purpose is to:

[0020]

According to the present invention, there is provided an illuminating apparatus comprising: a plurality of light sources; a light beam direction changing element for directing a traveling direction of light beams emitted from the plurality of light sources to a predetermined direction;
A lighting device comprising:
Each has a plurality of unit conversion elements provided corresponding to each of the plurality of light sources, and each of the plurality of light sources has an optical axis of a corresponding unit conversion element among the plurality of unit conversion elements. Arranged above, each of the plurality of unit conversion elements, a light ray incident from a corresponding light source among the plurality of light sources, and a light ray incident from at least one light source other than the corresponding light source, It has a first conversion region oriented in the predetermined direction, whereby the above object is achieved.

[0021] The first conversion area includes a light beam from the corresponding light source and at least one light beam adjacent to the corresponding light source.
A configuration may be such that light rays incident from the two light sources are directed in the predetermined direction.

[0022] Each of the plurality of unit conversion elements may be constituted by only the first conversion region.

[0023] Each of the plurality of unit conversion elements may further include a second conversion area for directing only light rays incident from the corresponding light source in the predetermined direction.

It is preferable that the second conversion area is provided at a position closer to the optical axis of the unit conversion element than the first conversion area.

[0025] The light beam direction conversion element may be a Fresnel lens, and each of the plurality of unit conversion elements may be a unit Fresnel lens.

[0026] The light beam direction conversion element may be a holographic element, and each of the plurality of unit conversion elements may be a unit holographic element.

The light beam direction changing element is a diffraction element,
Each of the plurality of unit conversion elements may be a unit diffraction element.

The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces are connected to the first conversion region. Having a first and a second prism surface inclined with respect to an optical axis of the unit Fresnel lens, at least a part of light rays incident on the first conversion region from the at least one adjacent light source,
By being refracted on the first prism surface, the light is directed in the predetermined direction, and at least a part of light rays incident on the first conversion region from the corresponding light source are refracted on the second prism surface. It may be configured to be directed in the predetermined direction.

The plurality of prism surfaces are formed on a surface of the unit Fresnel lens farther from the corresponding light source, and the first prism surface is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , the focal length of the unit Fresnel lens is f, When the distance between adjacent light sources is s and the relative refractive index of the unit Fresnel lens to the surrounding medium is n, θ
₁ and θ ₂ are θ ₁ = tan ⁻¹ ([{n ² f ² + (n ² −1) (sx) ² } ^{1/ 2-} {f ² + (sx) ² } ^1/2 ] / ( sx)) (1) θ ₂ = tan ^-1 ([{n ² f ² + (n ² -1) x ² } ¹ / ^2- (f ² + x ² ) ^1/2 ] / x) (2) Is preferably satisfied.

Alternatively, in a configuration in which the plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, the plurality of prism surfaces are located at a distance x from an optical axis of the unit Fresnel lens. The angle formed by the first prism surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , F is the focal length, s is the distance between adjacent light sources,
Assuming that the relative refractive index of the unit Fresnel lens with respect to the surrounding medium is n, θ ₁ and θ ₂ are θ ₁ = tan ⁻¹ ([n {f ² + (sx) ² } ^1/2 -f] / (sx)) (3) It is preferable to satisfy the relationship of θ ₂ = tan ⁻¹ [{n (f ² + x ² ) ^1/2 -f} / x] (4).

The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces are connected to the first conversion region. Having a first and a second prism surface inclined with respect to an optical axis of the unit Fresnel lens, at least a part of light rays incident on the first conversion region from the at least one adjacent light source,
At least a part of the light beam that is directed in the predetermined direction by being reflected by the first prism surface after being refracted on the second prism surface and incident on the first conversion region from the corresponding light source, is A configuration may be adopted in which the light is directed in the predetermined direction by refraction on the first prism surface.

The plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, and the first prism surface is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , the focal length of the unit Fresnel lens is f,
When the distance between adjacent light sources is s and the relative refractive index of the unit Fresnel lens with respect to the surrounding medium is n, θ ₁ and θ ₂ are expressed as follows: θ ₁ = (cos ⁻¹ [{f · cos θ ₂ − (sx ) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (5) θ ₂ = tan ^-1 [{n (f ² + x ² ) ^1/2 -f} / x] It is preferable to satisfy the relationship of (6).

The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces are connected to the first conversion region. Having a first and a second prism surface inclined with respect to an optical axis of the unit Fresnel lens, at least a part of light rays incident on the first conversion region from the at least one adjacent light source,
At least a part of the light beam that is directed in the predetermined direction by being reflected by the first prism surface after being refracted on the second prism surface and incident on the first conversion region from the corresponding light source, is The light may be directed in the predetermined direction by being reflected on the second prism surface after being refracted on the first prism surface.

The plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, and the first prism surface is located at a distance x from the optical axis of the unit Fresnel lens. The angle formed with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , the focal length of the unit Fresnel lens is f,
When the distance between adjacent light sources is s and the relative refractive index of the unit Fresnel lens with respect to the surrounding medium is n, θ ₁ and θ ₂ are expressed as follows: θ ₁ = (cos ⁻¹ [{f · cos θ ₂ − (sx ) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (7) θ ₂ = (cos ^-1 [{f ・ cos θ ₁ -x ・ sin θ ₁ } / n { f ² + x ² } ^1/2 ] -θ ₁ ) / 2 It is preferable to satisfy the relationship of (8).

The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces are connected to the first conversion region. A first, a second, a third, and a fourth prism surface inclined with respect to an optical axis of the unit Fresnel lens, and a part of a light beam incident on the first conversion region from the at least one adjacent light source. Is directed in the predetermined direction by being reflected by the first prism surface after being refracted on the second prism surface, and another part is refracted by the third prism surface after being refracted on the fourth prism surface. A part of the light beam which is directed in the predetermined direction by being reflected by the prism surface and which is incident on the first conversion area from the corresponding light source is the first prism. The other part is directed in the predetermined direction by being refracted on the third prism surface and then reflected on the fourth prism surface by being refracted on the third prism surface. At a position at a distance x from the optical axis of the unit Fresnel lens, the angle formed by the first prism surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , and the second prism surface is aligned with the optical axis of the unit Fresnel lens. ₂ an angle formed against theta, the angle of the third prism surface is formed with respect to the optical axis of the unit Fresnel lens theta _3, the fourth prism surface is formed with respect to the optical axis of the unit Fresnel lens When an angle is θ ₄ , a focal length of the unit Fresnel lens is f, a distance between adjacent light sources is s, and a relative refractive index of the unit Fresnel lens with respect to a surrounding medium is n, θ ₁ , θ ₂ ,
θ ₃ and θ ₄ are given by θ ₁ = (cos ⁻¹ [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (9 ^{_{) θ 2 = tan -1 [{}} n (f 2 + x 2) 1/2 -f} / x] (10) θ 3 = (cos -1 [{f · cosθ 4 - (sx) sinθ 4} / n {f ² + (sx) ² } ^1/2 ] -θ ₄ ) / 2 (11) θ ₄ = (cos ^-1 [{f ・ cos θ ₃ -x ・ sin θ ₃ } / n {f ² + x ² } ^1/2 ] -θ ₃ ) / 2 It is preferable to satisfy the relationship of (12).

Preferably, the first and second prism surfaces are provided in a region closer to the optical axis of the unit Fresnel lens than the third and fourth prism surfaces.

The unit Fresnel lens further has a second conversion area for directing only light rays incident from the corresponding light source in the predetermined direction, and the plurality of prism surfaces are provided on the second conversion area in the unit conversion area. The light source has a surface that is substantially parallel to the optical axis of the Fresnel lens and an inclined surface, and a light beam incident on the second conversion region from the corresponding light source is refracted on the inclined surface to thereby generate the predetermined light. It may be configured to be directed in the direction.

It is preferable that the second conversion area is provided at a position closer to the optical axis of the unit Fresnel lens than the first conversion area.

A display device according to the present invention includes any one of the above-described lighting devices and a display element that uses light emitted from the lighting device for display, thereby achieving the above object.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the structure and function of a lighting device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing the structure of a lighting device 10 according to an embodiment of the present invention. Lighting device 10
Is a light source device 11 and a light beam direction changing element 12 for directing a traveling direction of a light beam emitted from the light source device 11 in a predetermined direction.
And The light source device 11 includes a plurality of light sources 11a and 11b.
11c, and the beam direction converting element 12 includes a plurality of unit converting elements 12a, 12b and 12c. Each of unit conversion elements 12a, 12b, and 12c is provided corresponding to each of light sources 11a, 11b, and 11c. The light sources 11a, 11b and 11c are respectively provided with corresponding unit conversion elements 12a, 12b and 12c.
Are arranged on the respective optical axes OX. In the following, a plurality of light sources 11a, 11b, 11c,.
.. Are represented by the unit conversion element 12a.

The light source 11a is a linear light source extending in a direction perpendicular to the plane of FIG. 1 and is, for example, a fluorescent tube. Note that the light source 11a is not limited to a fluorescent tube, and may be, for example, an LED arranged linearly. Further, the plurality of light sources 11a do not need to be independent light sources. For example, the light source device 11 may be a light guide plate, and each light source 11a may be a part of a light guide. However, the light emitted from each of the plurality of light sources 11a is light that diffuses in the plane of the paper of FIG.

Each of the plurality of unit conversion elements 12a
At least one light source other than the light beam incident from the corresponding light source 11a and the corresponding light source 11a (11b and 1
1c) has a first conversion region M for directing a light beam incident from 1c) in a predetermined direction. Unit conversion element 12 shown in FIG.
Focusing on a, the unit conversion element 12a is composed of a light beam incident from the light source 11a and the light source 1 adjacent to both sides of the light source 11a.
It has a first conversion region M for directing a light beam incident from each of 1b and 11c in a predetermined direction. The first conversion region M of the unit conversion element 12a is typically formed on the side near the adjacent unit conversion regions 12b and 12c in the unit conversion element 12a, as shown in FIG.

As described above, each of the plurality of unit conversion elements 12a included in the light beam direction conversion element 12 of the illumination device 10 includes at least one light source (11b and 11b) other than the light beam incident from the corresponding light source 11a and the corresponding light source 11a. And / or 11c) has a first conversion region M for directing a light ray incident from the light source 11a in a predetermined direction, so that the characteristics (color tone and brightness of light) of the light source 11a and the light sources 11b and / or 11c are different. Also, the difference in characteristics between the light sources 11a and 11b or 11c is averaged by the first conversion region M. As a result, in the distribution of the intensity of the illumination light from the illumination device 10 (in the horizontal direction in FIG. 1), the boundary between the light sources 11a and 11b or 11c (or the boundary between the unit conversion elements 12a and 12b or 12c) is included. It does not appear and has a relatively uniform intensity distribution. Illumination light emitted by the illumination device 10 is typically parallel light, and its direction depends on the illumination device 1.
0 is a direction perpendicular to the emission surface 12E. Therefore, in the example of FIG. 1, the direction perpendicular to the emission surface 12E of the light beam direction conversion element 12 of the illumination device 10 is the “predetermined direction”.

In FIG. 1, a plurality of unit conversion elements 12
Although each of “a” has the first conversion region M on both sides, it is sufficient that at least one of the “a” has the first conversion region M. Further, the first conversion area M of the unit conversion element 12a is not limited to the one that converts light beams from the light sources 11b and 11c adjacent to the corresponding light source 11a in a predetermined direction, and converts light beams from other light sources into a predetermined direction. May be directed to Further, the first conversion area M does not necessarily need to be formed on both sides of the unit conversion element 12a (an area adjacent to the adjacent unit conversion elements 12b and / or 12c).

The unit conversion element 12a may further include, in addition to the above-described first conversion region M, a second conversion region S for directing only light rays incident from the corresponding light source 11a in a predetermined direction. As shown in FIG. 1, the second conversion area S
Is preferably provided at a position close to the optical axis OX of the unit conversion element 12a. That is, typically, it is provided between the two first conversion regions M formed at both ends of the unit conversion element 12a. Even in such a configuration, the distribution of the intensity of the illumination light from the illumination device 10 (in the horizontal direction in FIG. 1) is continuous, and no boundary appears. Needless to say, the unit conversion element 12a may be configured only of the first conversion area M without providing the second conversion area S in the unit conversion element 12a.

Typically, all unit conversion elements 12a
Have substantially the same configuration, but for example, the lighting device 10
The unit conversion elements 12a corresponding to the light sources 11a at both ends of
Since each is adjacent to only one unit conversion element 12a, the first conversion region M may be provided only on the side of the adjacent unit conversion element 12a.

In each case, a plurality of unit conversion elements 1
The elements 2a need not be independent elements, but may be formed integrally. For example, as shown in FIG. 1, the light beam direction changing element 12 is a Fresnel lens,
Each of the plurality of unit conversion elements 12a may be a unit Fresnel lens 12a. Alternatively, the light beam direction conversion element 12 may be a holographic element, and each of the plurality of unit conversion elements 12a may be a unit holographic element. Further, the light beam direction conversion element 12 may be a diffraction element, and each of the plurality of unit conversion elements 12a may be a unit diffraction element.

Hereinafter, the structure and function of an illuminating device including the light beam direction changing element 12 constituted by using a Fresnel lens will be described. First, in order to explain the structure and function of the first conversion region M included in the light beam direction conversion element 12 configured using a Fresnel lens, the structure and function of an illumination device including a Fresnel lens having only the first conversion region M will be described. Will be described.

The lighting device 20 shown in FIG. 2 has a plurality of light sources 11a and a plurality of unit Fresnel lenses 22a each having a first conversion area M. The light source 11a is arranged on each optical axis OX of the unit Fresnel lens 22a. The unit Fresnel lens 22a is
The surface (light receiving surface) 22R that receives light from a is flat, and the output surface 22E has a plurality of prism surfaces. That is,
The unit Fresnel lens 22a has a plurality of prism surfaces on a surface 22E farther from the light source 11a.

Referring to FIGS. 3A and 3B,
The structure and function of the unit Fresnel lens 22a will be described in more detail.

The plurality of prism surfaces formed on the exit surface 22E are provided in the first conversion region M in the unit Fresnel lens 22.
It has a first prism surface P1 and a second prism surface P2 inclined with respect to the optical axis OX of a. The light source (light source 11b or 11c in FIG. 1) adjacent to the light source 11a corresponding to the unit Fresnel lens 22a
At least a part of the light beam incident on the first conversion region M of the second prism 2a is directed in a predetermined direction by being refracted on the first prism surface P1, and is directed from the corresponding light source 11a to the first prism.
At least a part of the light beam incident on the conversion area M is refracted by the second prism surface P2 so as to be directed in a predetermined direction.
Each inclination angle of the prism surface P2 is set.
A prism having such a prism surface is called a refraction / refraction prism.

There are a plurality of first prism surfaces P1 and second prism surfaces P2, which are arranged alternately adjacent to each other, and the first prism surface P1 and the second prism surface P2 are arranged alternately.
The line of intersection with 2 forms the ridgeline of the prism surface. Also, the first
Angle of inclination θ _{1 between} prism surface P1 and second prism surface P2
And θ ₂ differ depending on the positions of the respective prism surfaces P1 and P2 from the optical axis OX.

The inclination angles θ ₁ and θ ₂ of the prism surfaces P1 and P2 are defined as angles relative to the optical axis OX in the plane of the paper of FIG. 2 (that is, in the plane perpendicular to the ridge line of the prism). As can be seen from FIG.
When the inclination angles θ ₁ and θ _{2 at} the position of the distance x from the optical axis OX of the unit Fresnel lens 22a satisfy the following formulas (1) and (2), the light from the light source emits the optical axis OX of the unit Fresnel lens 22a. Since the light is directed in a direction parallel to the direction, illumination light with high directivity can be obtained. In the following equation, f is the focal length of the unit Fresnel lens 22a, s is the distance between the adjacent light sources 11a, and n is the relative refractive index of the unit Fresnel lens with respect to the surrounding medium. Typically, the medium around the Fresnel lens is air, and the relative refractive index n matches the refractive index n ₀ of the Fresnel lens. The definitions of these parameters f, s, and n are common to the configurations described below.

Θ ₁ = tan ⁻¹ ([{n ² f ² + (n ² −1) (sx) ² } ^{1/ 2-} {f ² + (sx) ² } ^1/2 ] / (sx)) (1) θ ₂ = tan ^-1 ([{n ² f ² + (n ² -1) x ² } ¹ / ^2- (f ² + x ² ) ^1/2 ] / x) (2) Since the thickness of the unit Fresnel lens 22a is sufficiently small with respect to the distance from the unit Fresnel lens 22a to the unit Fresnel lens 22a, the distance between the light receiving surface 22R of the unit Fresnel lens 22a and the light source 11a is unitized in FIG. This is shown as being equal to the focal length f of the Fresnel lens 22a. Similar approximations are used in the following configurations.

Instead of the Fresnel lens 22 having the unit Fresnel lens 22a shown in FIGS. 2 and 3A,
A Fresnel lens including the unit Fresnel lens 22'a shown in FIG. 3B can be used.

The unit Fresnel lens 2 shown in FIG.
2'a indicates that the light-emitting surface 22'E is substantially flat and the light-receiving surface 2 '
2′R includes a first prism surface P1 and a second prism surface P2.
In the unit Fresnel lens 22′a, when the respective inclination angles θ1 and θ2 of the first prism surface P1 and the second prism surface P2 satisfy the following expressions (3) and (4), Since the light from the light source is directed in a direction parallel to the optical axis OX of the unit Fresnel lens 22'a, illumination light with high directivity can be obtained.

Θ ₁ = tan ⁻¹ ([n {f ² + (sx) ² } ^1/2 -f] / (sx)) (3) θ ₂ = tan ⁻¹ [{n (f ² + x ² ) ^1/2 -f} / x] (4) Next, the configuration and function of another illumination device 30 according to the present invention will be described with reference to FIGS.

The illumination device 30 shown in FIG. 4 has a plurality of light sources 11a and a plurality of unit Fresnellens 32a each having a first conversion region M. The light source 11a is arranged on each optical axis OX of the unit Fresnel lens 32a. The unit Fresnel lens 32a is
The surface (light receiving surface) 32R that receives light from the light source has a plurality of prism surfaces, and the emission surface 22E is flat.

The plurality of prism surfaces formed on the light receiving surface 32R are provided on the first conversion region M in the unit Fresnel lens 32R.
It has a first prism surface P1 and a second prism surface P2 inclined with respect to the optical axis OX of a. The light source adjacent to the light source 11a corresponding to the unit Fresnel lens 32a (the light source 11b or 11c in FIG.
At least a part of the light beam incident on the first conversion region M of 2a is directed in a predetermined direction by being refracted by the second prism surface P2 and then reflected by the first prism surface P1, from the corresponding light source 11a. First conversion area M
At least a part of the light beam incident on the first prism surface P
The respective inclination angles of the first prism surface P1 and the second prism surface P2 are set such that they are directed in a predetermined direction by being refracted at 1. A prism having such a prism surface is called a reflection / refraction prism.

As can be seen from FIG. 5, in the unit Fresnel lens 32a, the first prism surface P1 and the second
When the respective inclination angles θ1 and θ2 of the prism surface P2 satisfy the following expressions (5) and (6), the light rays from the light source are directed in a direction parallel to the optical axis OX of the unit Fresnel lens 32a, and thus are high. Directional illumination light is obtained.

Θ ₁ = (cos ⁻¹ [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (5) θ ₂ = tan ^-1 [{n (f ² + x ² ) ^1/2 -f} / x] (6) Next, referring to FIG. 6 and FIG. 7, the configuration and the configuration of still another illumination device 40 according to the present invention. The function will be described.

The illumination device 40 shown in FIG. 6 has a plurality of light sources 11a and a plurality of unit Fresnellens 42a each having a first conversion region M. The light source 11a is arranged on each optical axis OX of the unit Fresnel lens 42a. The unit Fresnel lens 42a is
The surface (light receiving surface) 42R that receives light from the light source has a plurality of prism surfaces, and the emission surface 22E is flat.

The plurality of prism surfaces formed on the light receiving surface 42R are provided in the first conversion area M in the unit Fresnel lens 42R.
It has a first prism surface P1 and a second prism surface P2 inclined with respect to the optical axis OX of a. The light source (light source 11b or 11c in FIG. 1) adjacent to the light source 11a corresponding to the unit Fresnel lens 42a
At least a part of the light beam incident on the first conversion region M of 2a is directed in a predetermined direction by being refracted by the second prism surface P2 and then reflected by the first prism surface P1, from the corresponding light source 11a. First conversion area M
At least a part of the light beam incident on the first prism surface P
After being refracted at 1 and reflected by the second prism surface P2, the first prism surface P2 is directed in a predetermined direction.
The respective inclination angles of the prism surface P1 and the second prism surface P2 are set. A prism having such a prism surface is called a reflection / reflection type prism.

As can be seen from FIG. 7, in this unit Fresnel lens 42a, the first prism surface P1 and the second prism
When the respective inclination angles θ1 and θ2 of the prism surface P2 satisfy the following expressions (7) and (8), the light rays from the light source are directed in a direction parallel to the optical axis OX of the unit Fresnel lens 42a, and thus are high. Directional illumination light is obtained.

Θ ₁ = (cos ⁻¹ [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] −θ ₂ ) / 2 (7) θ ₂ = (cos ^-1 [{f · cos θ ₁ -x · sin θ ₁ } / n {f ² + x ² } ^1/2 ] -θ ₁ ) / 2 (8) Note that the above-mentioned reflection / refraction type and reflection / reflection When both the mold and the mold are formed in the unit Fresnel lens, as will be described later, the reflective / reflective prism is formed near the boundary of the unit Fresnel lens, and the reflective / refractive prism is formed near the optical axis of the unit Fresnel lens. It is preferable to form it.

Here, a plurality of prism surfaces of the unit Fresnel lens are provided in the first conversion region M with first, second, third and fourth prism surfaces inclined with respect to the optical axis OX of the unit Fresnel lens. A portion of a light beam incident on the first conversion region from at least one adjacent light source is directed in a predetermined direction by being refracted by the second prism surface and then reflected by the first prism surface, Is directed in a predetermined direction by being refracted by the fourth prism surface and then reflected by the third prism surface, and a part of the light beam incident on the first conversion region M from the corresponding light source is Is directed in a predetermined direction by refraction on the first prism surface, and another part is refracted on the fourth prism surface after being refracted on the third prism surface. And directed to a predetermined direction. That is, the first prism surface and the second prism surface reflect /
It is assumed that a refraction prism is formed, and the third prism surface and the fourth prism surface form a reflection / reflection prism.

Then, at the position of the distance x from the optical axis OX of the unit Fresnel lens, the angle formed by the first prism surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , and the second prism surface is the light of the unit Fresnel lens. The angle formed with respect to the axis is θ ₂ , the angle formed by the third prism surface with respect to the optical axis of the unit Fresnel lens is θ ₃ , and the angle formed by the fourth prism surface with respect to the optical axis of the unit Fresnel lens is Assuming θ ₄ , θ ₁ , θ ₂ , θ ₃ and θ ₄ are given by θ ₁ = (cos ⁻¹ [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (9) θ ₂ = tan ^-1 [{n (f ² + x ² ) ^1/2 -f} / x] (10) θ ₃ = (cos ^-1 [{ _{f · cosθ 4 - (sx)} sinθ 4} / n {f 2 + (sx) 2} 1/2] -θ 4) / 2 (11) θ 4 = (cos -1 [{f · cosθ 3 -x・ Sin θ ₃ } / n {f ² + x ² } ^1/2 ] -θ ₃ ) / 2 By setting each angle so as to satisfy the relationship (12), highly directional illumination light is obtained. be able to.

Next, FIGS. 1, 8 (a) and 8 (b)
The structure and function of the second conversion region S of the unit Fresnel lens 12a will be described with reference to FIG. Note that the first conversion region M of the unit Fresnel lens 12a is one of the above-described refraction / refraction prism (FIG. 2), reflection / refraction prism (FIG. 4), and reflection / reflection prism (FIG. 6). Or a combination thereof.

The second conversion area S of the unit Fresnel lens 12a directs only a light beam incident from the corresponding light source 11a in a predetermined direction. As shown in FIG. 8A, the second conversion region S has a surface PP substantially parallel to the optical axis OX of the unit Fresnel lens 12a and a surface PI inclined, and the second light source 11a receives the second light from the corresponding light source 11a. The light ray incident on the two-conversion area S is directed in a predetermined direction by being refracted on the inclined plane PI. A prism having such a prism surface is called a refraction prism. Note that a prism having a plane PP parallel to the optical axis OX and an inclined plane PI is
This is similar to a prism formed on a conventional Fresnel lens.

As shown in FIG. 8A, when the prism surface is formed on the light receiving surface 12R, the inclined surface PI formed at a distance x from the optical axis OX of the unit Fresnel lens 12a is formed. When the inclination angle θ satisfies the following expression (13), the light from the light source is directed in a direction parallel to the optical axis OX of the unit Fresnel lens 12a, so that highly directional illumination light can be obtained.

Θ ≒ tan ⁻¹ [{n (f ² + x ² ) ^1/2 −f} / x] (13) Instead of the unit Fresnel lens 12 a, a refraction type as shown in FIG. A unit Fresnel lens 12'a having a prism formed on the emission surface 12E may be used. In this case, when the inclination angle θ of the inclined plane PI formed at a distance of x from the optical axis OX of the unit Fresnel lens 12′a satisfies the following expression (14), the light from the light source is unit Fresnel Since the light is directed in a direction parallel to the optical axis OX of the lens 12'a, illumination light with high directivity can be obtained.

Θ ≒ tan ⁻¹ ([{n ² f ² + (n ² −1) x ² } ¹ / ^2- (f ² + x ² ) ^1/2 ] / x) (14) FIG. 9 and FIG. The directivity of illumination light of an illumination device using each of the above-described refraction prism, reflection / refraction prism, and reflection / reflection prism will be described with reference to FIG. 9 and 10 show the results of the simulation, and assume a lighting device having the following configuration. FIG.
This corresponds to the result of measuring the intensity (for example, luminance) of the illumination light emitted at the position of the optical axis OX of the unit Fresnel lens for each emission angle. FIG. 10 shows the optical axis O of the unit Fresnel lens.
The intensity (for example, luminance) of the illumination light emitted in a direction parallel to X
Corresponds to the result of measurement for each distance from the optical axis OX.

In each of the illumination devices, a Fresnel lens having a prism surface formed on the surface facing the light source is used. The focal length f of each unit Fresnel lens of the Fresnel lens is set to １ ／ of the distance s between adjacent light sources (f = s / 2), and the Fresnel lens is made of a material having a refractive index n ₀ of 1.49. Use transparent acrylic resin. In each lighting device, the medium around the Fresnel lens is air, and the relative refractive index n of the Fresnel lens on each prism surface is equal to the refractive index n ₀ of the Fresnel lens (n = 1.49). The diameter of the cold cathode tube as a diffusion light source is 2.6 mm, the focal length f is 19 mm, and the distance s between adjacent light sources is 38 mm.

As can be seen from FIG. 9, it can be seen that the directivity of the illuminating light is very high at about ± 5 ° in all angles in any of the lighting devices. That is, it is understood that the Fresnel lens formed with any of the refraction prism, the reflection / refraction prism, and the reflection / reflection prism sufficiently controls the traveling direction of the light beam in a predetermined direction.

Also, from FIG. 10, in the vicinity of the optical axis of the unit Fresnel lens, the traveling direction of the light beam from the light source is efficiently controlled by the refraction prism or the reflection / refraction prism, and the amount of illumination light is large in the front direction. It can be seen that irradiation is performed. On the other hand, in the vicinity of the boundary with the adjacent unit Fresnel lens away from the optical axis, it can be understood that the traveling direction of the light beam is efficiently controlled by the reflection / reflection type prism, and that a large amount of illumination light is emitted in the front direction. In addition, if the refraction / refraction prism is formed in the first conversion region, it is possible to control the traveling directions of the light beams from two adjacent light sources,
Under the above-described conditions, the intensity of the illumination light emitted in the front direction is very small.

Therefore, a refraction prism forming the second conversion region is formed near the optical axis of the unit Fresnel lens, and a reflection / reflection type prism forming the first conversion region is formed near the boundary. The traveling direction of the light beam from the camera can be effectively controlled, and the illumination light is efficiently emitted in the front direction (parallel to the optical axis of the unit Fresnel lens). Furthermore, since the light from the light source corresponding to the unit Fresnel lens and the light from the adjacent light source are mixed and emitted from the first conversion region in which the reflection / reflection type prism is formed, the brightness and the brightness of the adjacent light source can be improved. Even if the color tone and the like are different from each other, uniform illumination light can be obtained without observing the boundary of the unit Fresnel lens.

Similarly, a reflection / refractive prism forming the first conversion region is formed near the optical axis of the unit Fresnel lens, and a reflection / reflection prism forming the first conversion region is formed near the boundary. Thus, the traveling direction of the light from the light source can be effectively controlled. When such a configuration is adopted, since the unit Fresnel lens is composed of only the first conversion region, the boundary of the unit Fresnel lens is more difficult to recognize as compared with the configuration having the second conversion region, and uniform illumination light can be generated. Obtainable.

Here, from the results of FIG. 10, under the above conditions (f = s / 2, n = 1.49), the refractive prism is located inside the position at a distance of 0.2 s from the optical axis. It is desirable that the reflection / reflection type prism is formed outside the position at a distance of 0.2 s from the optical axis, and similarly, the reflection / refraction type prism is formed inside the position at a distance from the optical axis of 0.2 s, The reflection / reflection type prism has a distance of 0.2 from the optical axis.
It can be seen that it is desirable to form it outside the position of s.

However, the arrangement of each prism can be appropriately set according to the focal length f of the unit Fresnel lens, the distance s between the light sources, and the refractive index n of the prism formed on the Fresnel lens. In particular, it is preferable to make s smaller than f from the viewpoint of uniformity of irradiation intensity. For example, as described above, when f = s / 2 and n = 1.49, the minimum value of the illumination light intensity is reduced to the maximum value of 60 by dividing the distance from the optical axis by 0.2 s. % (For example, see FIGS. 14 and 17).
However, by setting f> s / 2, the minimum value of the illumination light can be further increased. Conversely, when f <s / 2, the minimum value is 60% or less of the maximum value, and the intensity distribution of the illumination light becomes large. Therefore, the respective values of f, s, and n may be appropriately set according to the uniformity of the intensity allowed for the illumination light.

The above-described lighting device can be used as a backlight of a liquid crystal display device. Since the illumination device according to the present invention is an illumination device that emits illumination light having high directivity, it can be used, for example, as a backlight of a liquid crystal display device as described in Japanese Patent Application Laid-Open No. 2-118518. Wide viewing angle characteristics can be realized.

Further, the illumination device used in the liquid crystal display device has a polarization separation function, so that the light use efficiency can be improved. For example, an illumination device having a polarization separation function can be obtained by providing, on the emission surface side of the above-described illumination device, a polarization separation element that transmits polarized light applied to the liquid crystal element and reflects polarized light orthogonal to the polarized light. . As such a polarization separation element, for example, DBEF manufactured by Sumitomo 3M Limited is mentioned.

Hereinafter, specific embodiments according to the present invention will be described.

A liquid crystal display device 100 according to an embodiment of the present invention shown in FIG. 11 includes a lighting device (backlight) and a liquid crystal display element 120 receiving illumination light from the lighting device 110.
And a light diffusing element 130 provided on the viewer side of the liquid crystal display element 120.

The illuminating device 110 includes a plurality of linear light sources 111 arranged at equal intervals, and a reflecting sheet 112 provided on the back of the linear light source 111 (on the side opposite to the liquid crystal display element 120).
And a Fresnel lens 113.

The Fresnel lens 113 has a plurality of unit Fresnel lenses 113a, one unit Fresnel lens 113a is arranged so as to correspond to one linear light source 111, and each unit Fresnel lens 113a
Are formed linearly parallel to the linear light source 111. That is, the ridge lines of the plurality of prisms included in the unit Fresnel lens 113a extend in parallel with the linear light source 111. Each linear light source 111 is arranged near the focal point (correctly, a focal line) of the corresponding unit Fresnel lens 113a, and a light beam (diffused light) emitted from the linear light source 111 is output from the unit Fresnel lens 113a. Thus, the traveling direction is controlled, and illumination light having high directivity is emitted in the front direction. The reflection sheet 112 reflects the light from the linear light source 111 toward the Fresnel lens 113, thereby improving the light use efficiency. Depending on the type of the linear light source 111, the reflection sheet 112 can be omitted.

Next, the structure and function of the Fresnel lens 113 will be described with reference to FIG.

The Fresnel lens 113 has a prism surface formed on a surface (light receiving surface) near the light source 111, and has a first conversion area M near a boundary between the unit Fresnel lens 113a and the unit Fresnel lens 113a adjacent to the unit Fresnel lens 113a. Are formed, and a second conversion region S is formed near the optical axis OX of the unit Fresnel lens 113a. The first conversion area M of the unit Fresnel lens 113a is configured by a reflection / reflection type prism, and the second conversion area S is configured by a refraction type prism.

For the reflection / reflection type prism, the first inclination angle θ ₁ of the first prism surface P1 and the inclination angle θ ₂ of the second prism surface P2 were obtained in accordance with the above equations (7) and (8). In addition, in the refraction prism, the inclination angle θ of the surface inclined with respect to the optical axis OX of the unit Fresnel lens 113a is set in accordance with Expressions (13) and (14) described above.

In the present embodiment, the focal length f of the unit Fresnel lens 113a is set to 19 mm. Further, in order to configure the illumination device 110 having an illumination area of 400 mm × 300 mm, the linear light source 111 has an emission length of 400 mm.
Were arranged in parallel with each other, and the interval s between adjacent cold cathode tubes was 38 mm. An acrylic resin having a refractive index n of 1.49 is used as the material of the Fresnel lens 113,
It was formed by a hot press method. The Fresnel lens 113 has 8
The unit Fresnel lenses 113a are integrally formed. Further, the second conversion region S (refractive prism) is formed on the side closer to the optical axis OX than the position x where the distance x of the unit Fresnel lens 113a from the optical axis OX is 0.2 s, that is, 7.6 mm. A first conversion region M (reflection / reflection type prism) was formed.

As described above, the illumination device 110 has the refraction prism formed near the optical axis OX of the unit Fresnel lens 113a.
Since the reflection / reflection type prism is formed in the vicinity of the boundary with 13a, the traveling direction of the light beam from the linear light source 111 can be effectively converted to the front direction, and the illumination light in the unit Fresnel lens can be converted. The change in intensity is small. That is, the light source 1 corresponding to the light beam from the adjacent light source 111
11 is effectively directed in the front direction in the first conversion region, so that even if the brightness and / or the color tone of the adjacent light sources 111 are different from each other, the lighting device 110
The change of the brightness and / or color tone of the illumination light emitted from is smooth, and the boundary of the unit Fresnel lens 113a is not observed.

FIG. 13 shows the directivity of the illumination light of the illumination device 110.
FIG. 14 shows the change in the intensity of the illumination light in the unit Fresnel lens 113a. FIG. 13 shows the emission angle dependence of the intensity of the illumination light emitted at the position of the optical axis OX of the unit Fresnel lens 113a. FIG. 14 shows the dependence of the intensity of illumination light emitted in a direction parallel to the optical axis OX of the unit Fresnel lens 113a on the distance from the optical axis OX.

As can be seen from FIG.
Has the maximum intensity in the front direction (parallel to the optical axis of the unit Fresnel lens 113a = emission angle 0 °), and has a half value width of about ± 5 ° in full angle, which is extremely high directivity.
As can be seen from FIG. 14, the unit Fresnel lens 1
Although the intensity of the illumination light within 13a takes the maximum value on the optical axis OX, in the entire range of the unit Fresnel lens 113a,
An intensity of 60% or more of the maximum value is obtained.

Instead of the lighting device 110 shown in FIG.
The lighting device 210 shown in FIG. 15 may be used.

The illumination device 210 includes a Fresnel lens 213
Since the unit Fresnel lens 213a has substantially the same structure and function as the unit Fresnel lens 113a except for the unit Fresnel lens 113a, common components are denoted by the same reference numerals, and description thereof is omitted here.

The Fresnel lens 213 has a plurality of unit Fresnel lenses 213a, one unit Fresnel lens 213a is arranged so as to correspond to one linear light source 111, and each unit Fresnel lens 213a
Are linearly formed in parallel with the linear light source 111.
That is, the ridge lines of the plurality of prisms included in the unit Fresnel lens 213a extend in parallel with the linear light source 111.
Each linear light source 111 is arranged near the focal point (correctly, a focal line) of the corresponding unit Fresnel lens 213a, and a light beam (diffused light) emitted from the linear light source 111 is emitted from the unit Fresnel lens 213a. Thus, the traveling direction is controlled, and illumination light having high directivity is emitted in the front direction.

In the Fresnel lens 213, the light source 1
A prism surface is formed on a surface (light receiving surface) closer to 11 and a first conversion region M is formed over the entire region of the unit Fresnel lens 213a. A first conversion region M1 is formed near the optical axis OX of the unit Fresnel lens 213a, and a first conversion region M2 is formed near a boundary between the unit Fresnel lens 213a and the unit Fresnel lens 213a. . The first conversion region M1 is configured by a reflection / refraction prism, and the first conversion region M2
Is constituted by a reflection / reflection type prism.

Here, the prism surfaces of the reflection / refraction type prism forming the first conversion region M1 are defined as a first prism surface and a second prism surface, and the first conversion region M1 is supplied from an adjacent light source.
The light beam incident on the first prism surface is directed in a predetermined direction by being reflected by the first prism surface after being refracted on the second prism surface, and the light beam incident on the first conversion region M1 from the corresponding light source is: It is assumed that the light is directed in a predetermined direction by being refracted on the first prism surface.

Further, the reflection / constitution forming the first conversion region M2
The prism surfaces of the reflective prism are the third prism surface and the fourth prism surface, and the first conversion region M2
Are incident on the first conversion area M2 from the corresponding light source by being reflected by the third prism surface after being refracted on the fourth prism surface and reflected by the third prism surface. It is assumed that the light is directed in a predetermined direction by being refracted on the third prism surface and then reflected on the fourth prism surface.

The angles formed by the first, second, third and fourth prism surfaces defined above with respect to the optical axis OX of the unit Fresnel lens 213a are θ ₁ , θ ₂ , θ ₃ and θ, respectively. ₄ and then, so as to satisfy the above equation (9) to (12) were set each angle.

Note that, also in the present embodiment, the focal length f of the unit Fresnel lens 213a is set to 19 mm. In addition, an illumination device 21 having an illumination area of 400 mm × 300 mm.
In order to configure 0, the light emission length of the linear light source 111 is 4
Eight cold cathode tubes of 00 mm were arranged in parallel with each other, and the interval s between adjacent cold cathode tubes was 38 mm. The Fresnel lens 213 was formed by a hot press method using an acrylic resin having a refractive index n of 1.49. Fresnel lens 213
Is integrally formed with eight unit Fresnel lenses 213a. Further, the first conversion region M1 (reflection / refraction type prism) is formed closer to the optical axis OX than the position x where the distance x of the unit Fresnel lens 213a from the optical axis OX is 0.2 s, that is, 7.6 mm. The first conversion area M2 on the side
(Reflection / reflection type prism) was formed.

As described above, the illumination device 210 has the reflection / refractive prism formed near the optical axis OX of the unit Fresnel lens 113a, and the reflection / reflection type prism is formed near the boundary with the adjacent unit Fresnel lens 213a. Since the prism is formed, the traveling direction of the light beam from the linear light source 111 can be effectively converted to the front direction, and the change in the intensity of the illumination light within the unit Fresnel lens is small. That is, since the light from the adjacent light source 111 and the light from the corresponding light source 111 are effectively directed in the front direction in the first conversion area M (M1 and M2), the brightness and / or color tone of the adjacent light source 111 Even if they are different from each other, the change in luminance and / or color tone of the illumination light emitted from the illumination device 210 is smooth, and the boundary of the unit Fresnel lens 213a is not observed.

FIG. 16 shows the directivity of the illumination light of the illumination device 210.
FIG. 17 shows the change in the intensity of the illumination light in the unit Fresnel lens 213a. FIG. 16 and FIG.
14 and FIG.

As can be seen from FIG.
Has the maximum intensity in the front direction (parallel to the optical axis of the unit Fresnel lens 213a = emission angle 0 °), and has a half value width of about ± 5 ° in full angle, which is extremely high directivity.
Also, as can be seen from FIG. 17, the unit Fresnel lens 2
Although the intensity of the illumination light within 13a takes the maximum value on the optical axis OX, in the entire range of the unit Fresnel lens 213a,
An intensity of 60% or more of the maximum value is obtained.

Since the liquid crystal display device 100 of the present embodiment includes the illumination device 110, it is possible to provide an image with a small change in contrast ratio, halftone luminance, color tone, etc. in a wider viewing angle range than before.

As shown in FIG. 11, the liquid crystal display device 10
The liquid crystal display element 120 of 0 receives illumination light of high directivity from the illumination device 110. That is, the illuminating device 110 irradiates the liquid crystal display element 120 with illumination light having high directivity in the normal direction of the display surface. The liquid crystal display element 120 controls the light transmittance (luminance) by modulating the light emitted from the lighting device 110 for each pixel according to a display signal. The highly directional light transmitted through the liquid crystal display element 120 is diffused by the light diffusion element 130. Since the image observed by the observer is formed by light incident from the normal direction of the liquid crystal display element 120 and transmitted in the normal direction, changes in contrast ratio, halftone luminance, color tone, and the like in a wide viewing angle range. Few.

FIG. 18 shows a change in the contrast ratio of the liquid crystal display device 100 to which the lenticular lens film is applied as the light diffusing element 130 depending on the viewing angle. here,
A lenticular lens film having convex portions (pitch: 55 μm, height: 20 μm) like the light diffusion element 130 schematically shown in FIG. 11 was used.

As is clear from FIG. 18, a general conventional liquid crystal display device (for example, a TN mode liquid crystal display device having a conventional low directivity illumination device) has a sharp change in contrast ratio depending on the viewing angle. In contrast, it can be seen that the change in the contrast ratio of the liquid crystal display device 100 including the lighting device according to the present embodiment is reduced. Further, even when the lighting device 210 is used instead of the lighting device 110, display characteristics that are more excellent in viewing angle characteristics than the conventional liquid crystal display device are realized, similarly to the liquid crystal display device 100.

In the unit Fresnel lens 113a constituting the Fresnel lens 113, the positions where the first conversion region M and the second conversion region S are formed in order to effectively control the traveling direction of the light beam from the light source 111 (FIG. x) is the focal length f of the unit Fresnel lens 113a, the distance s between the adjacent light sources 111, and the refractive index n of the prism.
Therefore, it is set appropriately according to these values. Further, the first conversion regions M1 and M1 in the unit Fresnel lens 213a constituting the Fresnel lens 213
The position where 2 is formed also changes depending on the focal length f of the unit Fresnel lens 213a, the distance s between the adjacent light sources 111, and the refractive index n of the prism, and thus is appropriately set according to these values.

The prism formed in the unit Fresnel lens is not limited to the prism illustrated above, and at least the traveling direction of the light beam from the corresponding light source is controlled and emitted, and the traveling direction of the light beam from the adjacent light source is controlled. And a prism for emitting light. However, when a prism (a refraction prism in the unit Fresnel lens 113a) that controls and emits only the traveling direction of the light beam from the corresponding light source 111 is provided like the unit Fresnel lens 113a, Preferably, it is provided near the optical axis OX. The unit Fresnel lens 21
As shown in 3a, when a prism is provided to control and emit the light traveling from the corresponding light source over the entire unit Fresnel lens and emit the light while controlling the traveling direction of the light from the adjacent light source. It is preferable to provide a reflection / reflection type prism near the optical axis OX of the unit Fresnel lens and a reflection / reflection type prism near the boundary between adjacent unit Fresnel lenses. Note that a refraction / refraction prism can be used instead of the reflection / refraction prism. However, when a refraction / refraction type prism is used, it is preferable that the focal length f of the unit Fresnel lens is larger than the adjacent light source tube distance s. Refraction / refraction prisms are designed based on equations (1) and (2) above.

The Fresnel lens is not limited to an acrylic resin, and can be formed using various known transparent materials. However, a transparent resin such as an acrylic resin is preferable because it can be easily manufactured by a method such as an injection molding method or an extrusion molding method in addition to the hot press molding method described above, and is inexpensive and lightweight.

Other optical elements can be used in place of the Fresnel lens. For example, a diffraction element represented by a hologram element that controls the traveling direction by light diffraction can be used. Further, as the reflection sheet 112, a plane mirror is illustrated in the present embodiment, but a curved mirror may be used, for example.

The light diffusing element 130 provided on the viewer side of the liquid crystal display element 120 is not limited to the exemplified lenticular lens film, but may be an optical film processed into various shapes so as to diffuse light, or a light diffusing element. A scattering film or the like in which scattering particles are dispersed can be used. Further, a liquid crystal display element in which the light diffusing element is formed integrally (for example, formed integrally with a substrate arranged on the viewer side among a pair of substrates sandwiching the liquid crystal layer) can be used.

Further, when used as a lighting device for a liquid crystal display device, a polarizing beam splitter for selectively transmitting specific polarized light is provided on the light emitting side of the lighting device in order to improve the light use efficiency. Is also good. As the polarization separating element, for example, DBEF manufactured by Sumitomo 3M Limited can be used.

[0115]

According to the present invention, there is provided an illuminating device having high directivity and emitting illumination light having a uniform intensity distribution. Furthermore, by using the lighting device according to the present invention, a display device having a wide viewing angle characteristic can be provided. The lighting device according to the present invention is particularly effective for widening the viewing angle of a liquid crystal display device, but can be applied to other display devices. Further, the illumination device of the present invention can obtain uniform and highly-preferred illumination light using a plurality of light sources, and thus is suitably used for a large-sized display device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of a lighting device 10 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a structure of an illumination device 20 including a light beam direction changing element configured using a Fresnel lens.

FIG. 3A is a schematic diagram illustrating a structure of a unit Fresnel lens 22a included in the lighting device 20, and FIG. 3B is a schematic diagram illustrating a structure of a unit Fresnel lens 22′a that is a modification example thereof. .

FIG. 4 is a diagram schematically showing a structure of another lighting device 30 according to the embodiment of the present invention.

FIG. 5 shows a unit Fresnel lens 32 included in the lighting device 30;
It is a schematic diagram which shows the structure of a.

FIG. 6 is a diagram schematically showing a structure of another illumination device 40 according to the embodiment of the present invention.

FIG. 7 shows a unit Fresnel lens 42 included in the illumination device 40.
It is a schematic diagram which shows the structure of a.

FIG. 8A shows a Fresnel lens 12 of the illumination device 10;
FIG. 4 is a schematic diagram showing a structure of a second conversion region S of a unit Fresnel lens 12a included in (a), and (b) is a schematic diagram showing a structure of a second conversion region S of a unit Fresnel lens 12′a which is a modified example thereof. .

FIG. 9 is a graph showing the directivity of illumination light of an illumination device using a Fresnel lens including a refractive prism, a reflective / refractive prism, and a reflective / reflective prism.

FIG. 10 shows the relationship between the illumination light in the unit Fresnel lens of the refraction prism, the reflection / refraction prism, and the Fresnel lens including the reflection / reflection prism used in the illumination device from which the illumination light shown in FIG. 9 was obtained. It is a graph which shows intensity change.

FIG. 11 is a liquid crystal display device 100 according to an embodiment of the present invention.
It is a schematic diagram which shows the structure of.

FIG. 12 shows a lighting device 110 included in the liquid crystal display device 100.
It is a schematic diagram which shows the structure of.

FIG. 13 is a graph showing the directivity of illumination light from the illumination device 110.

FIG. 14 is a graph showing a change in intensity of illumination light in a unit Fresnel lens 113a included in the illumination device 110.

FIG. 15 is a schematic diagram showing a configuration of another illumination device 210 used in the liquid crystal display device 100.

FIG. 16 is a graph showing the directivity of illumination light from the illumination device 210.

FIG. 17 is a graph showing a change in intensity of illumination light in a unit Fresnel lens 213a included in the illumination device 210.

FIG. 18 is a graph showing a change in contrast ratio of the liquid crystal display device 100 depending on a viewing angle.

FIG. 19 is a diagram schematically showing a conventional liquid crystal display device 300 using an illumination device provided with a Fresnel lens.

FIG. 20 is a schematic diagram for explaining a conventional Fresnel lens.

FIG. 21 is a diagram schematically illustrating a conventional lighting device 410 including a total internal reflection (TIR) lens.

FIG. 22 is a diagram for explaining a problem of a lighting device configured using a conventional Fresnel lens.

FIG. 23 is a diagram for explaining a problem of a lighting device configured using a conventional total internal reflection (TIR) lens.

[Explanation of symbols]

10, 20, 30, 40, 110, 210 Illuminating device 11 Light source device 11a Light source 12, 22, 32, 42 Fresnel lens 12a, 12b, 12c, 22a, 32a, 42a Unit Fresnel lens 111 Linear light source 112 Reflecting sheet 113, 213 Fresnel lens 113a, 213a Unit Fresnel lens 120 Liquid crystal display element 130 Light diffusion element 213 Fresnel lens 220 Liquid crystal display element 230 Light diffusion means 300 Liquid crystal display apparatus 310, 410 Illumination apparatus 311 311 'Light source 312 Spherical mirror 311' Light source 313, 313 'Fresnel lens 313'a Unit Fresnel lens 320 Liquid crystal display element 330 Light diffusing element 411, 411' Light source 412, 412 'Total internal reflection (TIR) lens 412'a Unit total internal reflection (TIR) lens

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 5/18 G02B 5/18 5/32 5/32 G02F 1/1335 G02F 1/1335 1/13357 1 / 13357 // F21Y 101: 02 F21Y 101: 02 103: 00 103: 00

Claims (20)

[Claims] 1. An illumination device comprising: a plurality of light sources; and a light beam direction changing element for directing a traveling direction of a light beam emitted from the plurality of light sources to a predetermined direction. Has a plurality of unit conversion elements provided corresponding to each of the plurality of light sources, and each of the plurality of light sources is on an optical axis of a corresponding one of the plurality of unit conversion elements. Each of the plurality of unit conversion elements, a light ray incident from a corresponding light source among the plurality of light sources, and a light ray incident from at least one light source other than the corresponding light source, An illumination device having a first conversion area oriented in a predetermined direction. 2. The method according to claim 1, wherein the first conversion area directs a light ray from the corresponding light source and a light ray incident from at least one light source adjacent to the corresponding light source in the predetermined direction. The lighting device according to any one of the preceding claims. 3. Each of the plurality of unit conversion elements,
The lighting device according to claim 1, wherein the lighting device includes only the first conversion region. 4. Each of the plurality of unit conversion elements includes:
The lighting device according to claim 1, further comprising a second conversion region that directs only light rays incident from the corresponding light source in the predetermined direction. 5. The lighting device according to claim 4, wherein the second conversion area is provided at a position closer to an optical axis of the unit conversion element than the first conversion area. 6. The lighting device according to claim 1, wherein the light beam direction conversion element is a Fresnel lens, and each of the plurality of unit conversion elements is a unit Fresnel lens. 7. The lighting device according to claim 1, wherein the light beam direction conversion element is a holographic element, and each of the plurality of unit conversion elements is a unit holographic element. 8. The illumination device according to claim 1, wherein the light beam direction conversion element is a diffraction element, and each of the plurality of unit conversion elements is a unit diffraction element. 9. The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces is the first conversion surface. The region has first and second prism surfaces inclined with respect to the optical axis of the unit Fresnel lens, and at least a part of light rays incident on the first conversion region from the at least one adjacent light source are The light is directed in the predetermined direction by being refracted on the first prism surface, and at least a part of the light beam incident on the first conversion region from the corresponding light source is refracted on the second prism surface. The lighting device according to claim 2, wherein the lighting device is oriented in a predetermined direction. 10. The plurality of prism surfaces are formed on a surface of the unit Fresnel lens farther from the corresponding light source, and the first prism is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed by the surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , and the focal length of the unit Fresnel lens is f, the distance between adjacent light sources is s, and the relative refractive index of the unit Fresnel lens to the surrounding medium is n, and θ ₁ and θ ₂
Is θ ₁ = tan ^-1 ([{n ² f ² + (n ² -1) (sx) ² } ^{1/ 2-} {f ² + (sx) ² } ^1/2 ] / (sx)) ( 1) θ ₂ = tan ^-1 ([{n ² f ² + (n ² -1) x ² } ¹ / ^2- (f ² + x ² ) ^1/2 ] / x) The lighting device according to claim 9, wherein: 11. The plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, and the first prism is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed by the surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , and the focal length of the unit Fresnel lens is f, the distance between adjacent light sources is s, and the relative refractive index of the unit Fresnel lens with respect to the surrounding medium is n, and θ ₁ and θ ₂
Is θ ₁ = tan ^-1 ([n {f ² + (sx) ² } ^1/2 -f] / (sx)) (3) θ ₂ = tan ^-1 [{n (f ² + x ² ) The lighting device according to claim 9, which satisfies the relationship of ¹ / ^2- f} / x] (4). 12. The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces is the first conversion surface. The region has first and second prism surfaces inclined with respect to the optical axis of the unit Fresnel lens, and at least a part of light rays incident on the first conversion region from the at least one adjacent light source are After being refracted on the second prism surface and reflected by the first prism surface, the light is directed in the predetermined direction, and at least a part of the light beam incident on the first conversion region from the corresponding light source is the second light source. The lighting device according to claim 2, wherein the illumination device is directed in the predetermined direction by refracting the light on one prism surface. 13. The plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, and the first prism is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed by the surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , and the focal length of the unit Fresnel lens is f, the distance between adjacent light sources is s, and the relative refractive index of the unit Fresnel lens to the surrounding medium is n, and θ ₁ and θ ₂
Is θ ₁ = (cos ^-1 [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (5) θ ₂ = tan The lighting device according to claim 12, which satisfies the following relationship: ^-1 [{n (f ² + x ² ) ^1/2 -f} / x] (6). 14. The light beam direction conversion element is a Fresnel lens, each of the plurality of unit conversion elements is a unit Fresnel lens having a plurality of prism surfaces, and the plurality of prism surfaces is the first conversion surface. The region has first and second prism surfaces inclined with respect to the optical axis of the unit Fresnel lens, and at least a part of light rays incident on the first conversion region from the at least one adjacent light source are After being refracted on the second prism surface and reflected by the first prism surface, the light is directed in the predetermined direction, and at least a part of the light beam incident on the first conversion region from the corresponding light source is the second light source. The illumination device according to claim 2, wherein the light is directed in the predetermined direction by being refracted on one prism surface and then reflected on the second prism surface. Lighting device. 15. The plurality of prism surfaces are formed on a surface of the unit Fresnel lens closer to the corresponding light source, and the first prism is located at a distance x from an optical axis of the unit Fresnel lens. The angle formed by the surface with respect to the optical axis of the unit Fresnel lens is θ ₁ , the angle formed by the second prism surface with respect to the optical axis of the unit Fresnel lens is θ ₂ , and the focal length of the unit Fresnel lens is f, the distance between adjacent light sources is s, and the relative refractive index of the unit Fresnel lens with respect to the surrounding medium is n, and θ ₁ and θ ₂
Is θ ₁ = (cos ^-1 [{f · cos θ _2- (sx) sin θ ₂ } / n {f ² + (sx) ² } ^1/2 ] -θ ₂ ) / 2 (7) θ ₂ = ( The lighting according to claim 14, which satisfies the relationship of cos ^-1 [{f · cos θ ₁ -x · sin θ ₁ } / n {f ² + x ² } ^1/2 ] -θ ₁ ) / 2 (8). apparatus. 16. The light beam direction changing element is Fresnellen.
Wherein each of the plurality of unit conversion elements is
A unit Fresnel lens having a number of prism surfaces, wherein the plurality of prism surfaces are arranged in the first conversion region.
First, second, inclined with respect to the optical axis of the
Third and fourth prism surfaces, wherein the at least one adjacent light source receives the first conversion area.
Some of the light rays incident on the area are incident on the second prism surface.
Reflected by the first prism surface after being refracted
Is directed in the predetermined direction by the other part
Is refracted on the fourth prism surface,
The predetermined light is reflected by the three prism surfaces.
And light rays incident on the first conversion area from the corresponding light source
Is partially refracted on the first prism surface.
Is oriented in the predetermined direction, and another part is
The fourth prism after being refracted on the third prism surface
Reflected in the predetermined direction by being reflected by the
At a distance x from the optical axis of the unit Fresnel lens.
And the first prism surface is the light of the unit Fresnel lens.
The angle formed with respect to the axis is θ₁The second prism surface is
The angle formed with respect to the optical axis of the unit Fresnel lens is
θ_Two, The third prism surface is the unit Fresnel lens
The angle formed with the optical axis is θ_Three, The fourth prism surface
Is formed with respect to the optical axis of the unit Fresnel lens
To θ_Four, The focal length of the unit Fresnel lens is f
S is the distance between adjacent light sources, and the unit
When the relative refractive index of the Rennel lens is n, θ₁, Θ_Two,
θ _ThreeAnd θ_FourIs θ₁= (Cos^-1[{f ・ cosθ_Two-(s-x) sinθ_Two} / n {f^Two+ (s-x)^Two}^1/2] -θ_Two) / 2 (9) θ_Two= Tan^-1[{n (f^Two+ x^Two)^1/2-f} / x] (10) θ_Three= (Cos^-1[{f ・ cosθ_Four-(s-x) sinθ_Four} / n {f^Two+ (s-x)^Two}^1/2] -θ_Four) / 2 (11) θ_Four= (Cos^-1[{f ・ cosθ_Three-x ・ sinθ_Three} / n {f^Two+ x^Two}^1/2] -θ_ThreeThe lighting device according to claim 2, which satisfies the relationship of (2) / 2). 17. The device according to claim 16, wherein the first and second prism surfaces are provided in a region closer to an optical axis of the unit Fresnel lens than the third and fourth prism surfaces.
The lighting device according to claim 1. 18. The unit Fresnel lens further includes a second conversion area that directs only light rays incident from the corresponding light source in the predetermined direction, wherein the plurality of prism surfaces are arranged in the second conversion area. The unit Fresnel lens has a surface that is substantially parallel to the optical axis and an inclined surface, and a light beam incident on the second conversion region from the corresponding light source is refracted on the inclined surface. The lighting device according to any one of claims 9 to 17, which is oriented in a predetermined direction. 19. The lighting device according to claim 18, wherein the second conversion area is provided at a position closer to an optical axis of the unit Fresnel lens than the first conversion area. 20. A display device, comprising: the lighting device according to claim 1; and a display element that uses light emitted from the lighting device for display.